When a light-emitting diode is formed by using a chip-shaped semiconductor light-emitting device in which a light-emitting layer and an electrode layer are formed on a semiconductor substrate, it is a common practice to use a package having a recessed portion (see Literature 1: the published Japanese patent application 2002-232017). The package described in Literature 1 uses the bottom surface of the recessed portion as a mounting portion for mounting a semiconductor light-emitting device to allow light emitted from the semiconductor light-emitting device to emerge from the opening of the recessed portion to the outside.
In the package of Literature 1 above, to increase the luminous efficiency of the light-emitting diode, not only is the recessed portion formed to have a shape extending toward outside from the bottom surface to the opening (a conical shape) but also the inner surface of the recessed portion is covered with a metal layer capable of reflecting the light emitted from the semiconductor light-emitting device.
A light-emitting diode is produced by the following process. First, a semiconductor light-emitting device is mounted on the mounting portion of the package. The recessed portion is filled with a fluorescent body and/or protective resin to seal the semiconductor light-emitting device. The opening is closed with a sealing cap or lens as required.
On the other hand, a surface light-emitting body is formed by the following process. First, a plurality of mounting portions for mounting a semiconductor light-emitting device are formed on one substrate. A semiconductor light-emitting device is mounted on each of the mounting portions. The semiconductor light-emitting devices are sealed with a fluorescent body and/or protective resin. (see Literature 2: the published Japanese patent application 2001-332769).
In the case of a semiconductor light-emitting device, it is difficult to distinguish a satisfactory device from an unsatisfactory device at the stage of a chip. Consequently, in the case of a light-emitting diode, it is a common practice to employ the following procedure. First, the semiconductor light-emitting device is mounted on the mounting portion of the package using adhesive or solder and electrically connected with wire bonding or another means. Subsequently, a quality examination test is performed to see whether the device emits light or not, the emitted light has a specified wavelength or not, and so on.
In particular, in the case of, for example, a white-light-emitting diode that achieves white light by combining a semiconductor light-emitting device for emitting light having a specified wavelength and a fluorescent body, it is a common practice to employ the above-described procedure. That is, first, the semiconductor light-emitting device is mounted on the mounting portion of the package. Then, the recessed portion of the package is filled with a specified quantity of a fluorescent body. Subsequently, a quality examination test is performed to see whether the device emits light or not, the emitted light has a specified shade of color or not, and so on.
As a result, if the semiconductor light-emitting device is unsatisfactory so that it does not emit light at all or it cannot emit specified light because the light has a largely deviated wavelength, the used package and fluorescent body become wasted completely, which is a problem.
In addition, when the semiconductor light-emitting device is mounted on the package, unsatisfactory wiring may occur and the device may be broken due to static electricity, heat, or the like. If these faults occur, the used package and fluorescent body also become wasted completely, which is another problem.
In particular, in recent years, to increase the luminous efficiency of a light-emitting diode, it has been becoming a common practice to use a package having a complex structure as described in Literature 1 above or to use a costly highly heat-dissipative member in a package to respond to the increase in the output of a light-emitting diode. Consequently, when a package becomes a waste, a large amount of economical loss will be caused, which is a problem.
The production of a surface light-emitting body, also, suffers a similar problem. More specifically, it is a common practice to employ the following procedure. First, the semiconductor light-emitting device is mounted on the mounting portion of the substrate using adhesive, solder, or the like and electrically connected with wire bonding or another means. Subsequently, a quality examination test is performed to see whether the device emits light or not, the emitted light has a specified wavelength or not, and so on.
In particular, in the case of a white-surface-light-emitting body that achieves white light by combining a semiconductor light-emitting device for emitting light having a specified wavelength and a fluorescent body, it is a common practice to employ the following procedure. First, a plurality of semiconductor light-emitting devices are mounted on the substrate as described above. Second, each semiconductor light-emitting device is sealed with a specified quantity of a fluorescent body. Then, a quality examination test is performed to see whether the device emits light or not, the emitted light has a specified shade of color or not, and so on.
Consequently, even if one of the multiple semiconductor light-emitting devices mounted on the substrate becomes unsatisfactory, i.e., it does not emit light or it cannot emit the specified white light because the light has a deviated wavelength, all the following components become wasted: all the other semiconductor light-emitting devices, the fluorescent bodies used for sealing the individual semiconductor light-emitting devices, and the substrate on which the circuit for driving the individual semiconductor light-emitting devices is formed. As a result, a large amount of economical loss will be caused, which is a problem.
In addition, it is unavoidable for individual semiconductor light-emitting devices to emit light having a deviated wavelength. Therefore, it is ideal to select the multiple semiconductor light-emitting devices to be used in the same surface light-emitting body in advance so that the variation in wavelength of the light they emit can be minimized to obtain a uniform property. However, as described above, it is difficult to examine the wavelength of the light emitted from conventional semiconductor light-emitting devices. As a result, the variation in the shade of color tends to be produced in the light emitted from a surface light-emitting body, which is another problem.
Furthermore, the package described in Literature 1 is formed by the cofire method, whose process is explained below. First, a ceramic green sheet is prepared as the starting material of the ceramic material for forming the package. The ceramic green sheet is provided with a recessed portion, via, through hole, and the like. Subsequently, the above-described metal layer, the metalized layer to be used as an electrode layer for mounting the device, the via, the through hole, and so on are formed in a specified shape using an electrically conductive paste containing a high-melting-point metal, such as Mo and W. Finally, the entire formed body is sintered.
In the cofire method, however, when sintered at high temperature, the ceramic green sheet shrinks. Therefore, it is difficult to form the via, through hole, metalized layer, and the like with high precision. In particular, a small package and a package having a minute metalized pattern cannot be produced with high yield, which is a problem.
In addition, the metallic layer and electrode layer are structured by stacking a surface layer having good reflectivity to light and good electrical conductivity on the metalized layer using the plating method. In this case, an aluminum surface layer is particularly suitable as the surface layer for the metal layer because it has good reflectivity to the light having a short wavelength suitable for producing white light by combining with a fluorescent body. However, it is difficult to form the aluminum surface layer on the metalized layer by the plating method, which is another problem.